Infection and Immunity III

Infection and Immunity III - BIO/MI 494G INFECTION AND...

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BIO/MI 494G INFECTION AND IMMUNITY FALL 2008 I. Pattern recognition receptors (PRRs) on phagocytes with specificity for pathogen associated molecular patterns (PAMPs) 1. Introduction a. PRRs b. PAMPs 2. Comparison of the characteristics of recognition molecules of innate and adaptive immune systems 3. PRRs on phagocytes and their ligands (PAMPs) on microbes a. Function b. Examples of PRRs and PAMPs i. Seven transmembrane α -helical receptors ii. Mannose receptors iii. Scavenger receptors iv. Receptors for opsonins v. Receptors for complement components vi. Toll-like receptors II. Phagocytosis of microorganism 1. Cellular steps in phagocytosis a. Chemotaxis b. Attachment c. Ingestion d. Digestion 2. Mechanisms responsible for killing phagocytosed pathogens a. Respiratory burst-formation of reactive O 2 intermediates b. Nitric oxide formation III. Activated macrophages secrete a variety of cytokines important in inflammation 1. Local and systemic effects
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Table 12-1. Specificity of Innate and Adaptive Immunity I Innate immunity I~A-d-a-p-ti-v-e-i-m-m-u-n-i-ty----I For structures shared by classes of For structural detail of microbial microbes ("molecular patterns") SpecifiCity molecules (antigens); may recognize nonmicrobial aliltigerls Different --J : D~fferent -r JL, *: microbes L 'm,erobes L ;l-.JI{J/!II ~ -' Identical ---I mannose L [ D;stinctA ~ ;( ~ ! receptors i antibody ; : molecules ' ~ ... -_ .... ~. __ .. _..: ..... __ ~. ....... ~ __ .~ ...... __ ..: Encoded in germline; limited diversity Encoded by geoos produced by somatic recombination of gene segments; greater diversity Receptors ,.------ .. -.------ .... - .... ---. -"1 r'··-·····--··----· .. --------1 I Ii fi;! ! II I , ! I , ! LPS N-focmyt- , l'~ I I receptor methionyi Mannose Scavenger I i L receptor _~~=:tor receptor_l _ .. . ' ... .J Nonclonal: identical receptors on Clonal: clones of lymphocytes all cells of the same lineage with distinct specificities express Distribution . ,of receptors. different receptors Discrimination Yes; host cells are not recognized or they Yes; based on selection against of self and ." .' may express molecules that prevent innate self-reactive l~mPhocytes; may nonself immune reactions ~ imperfect giving rise to autoimmunity .... .... __ .. __ .~~_._. _·· .. __ ~.'4 __
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Specificity inherited in the genome Yes Expressed by all cells of a particular type (eg, macrophages) Triggers immediate response Yes Yes Recognizes broad classes of pathogen Yes Interacts with a range of molecular structures of a given type Encoded in multiple gene segments Requires gene rearrangement Clonal distribution Able to discriminate between even closely related molecular structures Fig. 2.10 Comparison of the characteristics of recognition molecules of the innate and adaptive Immune systems. The innate immune system uses receptors that are encoded by complete genes inherited through the germline, whereas the adaptive immune system uses antigen receptors encoded in gene segments that are assembled into complete T-cell and B-cell receptor genes during lymphocyte development, a process that leads to each individual cell expressing a receptor of unique specificity. As a result, receptors of the innate immune system are deployed nonclonally (that is, by all the cells of
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